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| Reviews Summary for Pyramid PS-53KX Power Supply |
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Reviews: 11
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Average rating: 2.1/5
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MSRP: $257.00
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Description: 53 amps peak, 12-15 VDC power supply w/thermal and overvoltage protection.
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More info: http://
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W6EM
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Rating: 1/5
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Nov 2, 2009 15:59
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Needs Rework.......
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Time owned: more than 12 months
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I did 3/4 of what WB4FUR did to my PS-52KX, and I'm not finished.
The ballast resistors, if 0.1 ohm units are used, limits the current to just about 5 amperes per transistor. 8 times 5 is 40 amps. Better to reduce them somewhat to about .08 to be able to realize the 52 amps.
And, the jumper from the junction of all of the emitter wires terminates in one No. 12 going to the red terminal. Imagine how hot a No. 12 wire will get with upwards of 50 amps on it.
The crowbar circuits in this and another Pyramid I have leave a lot to be desired. Traces won't handle short circuit currents well above the rated currents of the supplies. Get bigger SCRs and wire them so they can take probably more than 100 amps for a few milliseconds til a real fuse blows, not the board trace.
I'm going to use an SCR rated for about 40 amps continuous with an I squared t of about 1600 since it has to last long enough to open the AC line fuse.
One of the reasons Astrons last is that they have transient overvoltage protection on the LM723 regulator and Pyramid doesn't. The 723s will pop just above 40 volts, so if their inputs aren't clamped with a zener, well....... Also, Astron uses a TVSS on the transformer too.
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NF3Q
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Rating: 2/5
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Oct 26, 2009 16:51
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As the numerical rating says... "Needs Help"
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Time owned: 0 to 3 months
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I too have one for repeater service, and fortunately, it was shut off before it had a chance to do any damage. I had a small short (my error) and instead of the supply shutting off, it took out the regulator and decided to soar to 24-25 VDC as well. While I agree that it was poorly designed, I concur with WB4FUR and his remarks about this supply having great potential. I fully anticipate rehabilitating mine and also want to go on the record-- beware if you purchase this unit and intend on using it with any expensive equipment, especially repeaters. Best of luck!
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KG8FV
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Rating: 1/5
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May 9, 2009 18:39
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Poor quality
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Time owned: more than 12 months
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This power supply is not made for repeater use! BEWARE! use a ASTRON instead!. The rectifiers are 35 amps so giving you a 70 amp surge well at 50 amps you only have 20 amp lea way. Mine blew up went 24 dc and ran away! blew up my controller. I got the supply fixed ran 5 month and went out again! this time around I'm going to put in the TWO 50 AMP rectifiers!. So we can get more backup. But this thing is just for normal use it would probably be ok but in a repeater environment no way!
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KE7FFM
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Rating: 5/5
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May 2, 2009 22:09
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10 years and going strong!
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Time owned: more than 12 months
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10years with the ps-52kx. i have charged car battereis to run ham gear. I have shorted the output manytimes,, and abused in about eery way possible. still going strong, no repairs so far !!
also, when checking for ripple the scope trace looks clean, even after ten years of rough service. are many componets undersize? i ouwl think so, and yet I have ran mine at full output current for long time periods, and given it a workout on a daily basis. If this one quits, I'll rebuild it or buy a new one in a minute!
last poster must be an engineer, there never happy unless they make their own!!
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N3OQD
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Rating: 1/5
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Aug 12, 2008 10:42
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Badly in need of many mods
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Time owned: 6 to 12 months
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Just an update to my PS-52KX. After reading the statements by WB4FUR, I decided to look into modding my set as well. Unbeknownst to me, when I looked down into the set at the control circuit board I knoticed R13 (10 ohm) resistor was burned up. Opon further examination I found that the tiny (Z-1) 16v Zener was bad also. Also the tiny foil trace that connected to the Anode was burnt open as well. How in the hell does the engineer of this set think that this punny, so called "Crow bar overvoltage protection" would even work once? Yea right! That tiny trace that opened up is supposed to carry the clamping current of over 50 amps? The only reason why I now give it a rating of 1 is that there is hope. One at least has a platform to build off of. Since it does (miraculusly) work at the present, I am temporarly using it soley to charge my 100 amp hour AGM battery. After fully charging, I then disconect it from the power supply and re-connect my radios to the battery itself. In this, the radios are not connected to the power supply and not at risk. In the mean time, I am collecting the parts needed as WB4FUR has stated including adding a socket for the LM723 control IC. I'm doing the work myself. If anyone reading this needs a schematic, I do have a photo immage of this model and the larger PS-64KX. Just e-mail me at n3oqd@juno.com In retrospect, I am stuck with this lemon and now to make lemonaide. Avoid this product completely and opt for an iron based Astron linear power supply instead. It is a far better product for just a few dollars more.
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WB4FUR
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Rating: 0/5
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May 12, 2008 18:01
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Piece of junk, but can be made better
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Time owned: 0 to 3 months
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All: I purchased one of these at a hamfest in non-working condition. Opening the case and studying the schematic shows why.
The power transformer sure appears to be something that would deliver the goods. Heavy iron. I don't know if it would get to 50A continuous or not, but there's at least hope. Grade: B
The rectifiers are 35-ampere bridge rectifiers. Diodes in parallel. If there's any mismatch in the diodes, one winds up taking all the current, and it fails. That's what had happened in mine. Grade: F
The pass transistors are mounted on good heatsinks, cooled with a small fan. Collectors are bonded together with metal straps. Unclear if they can dissipate the heat under full load, but there's hope. Individual emitter connections to a common point. Grade: B
NO CURRENT-BALANCING EMITTER RESISTORS. Worst possible design decision. Grade: F-----...
Electrolytics are small, PC-board mount devices, with small-gauge wire connecting rectifiers, caps, and rest of circuit. Grade: D-
Crowbar SCR is small, 16-ampere unit. Could not possibly handle crowbar current more than once! SCR is PC-board mounted (HOW did they expect it to handle the current????). Grade: F-----...
If you own one of these, you could bring it to being a first-rate supply as follows:
a. Replace the rectifiers with stud-mount, 85-ampere units (Mouser has them). I did this; took a few minutes with a drill to enlarge the mounting holes for the original rectifiers.
b. Replace the electrolytics with large, PC-grade caps, and run heavy-gauge (10 AWG or better) from the two diodes to the caps, and from the caps to the pass transistor collectors. You need the large caps to be able to land heavy-gauge wire.
c. Install 0.1 ohm emitter resistors on each of the 8 pass transistors. I was going to use cased wirewounds that would mount against the heat sinks (again from Mouser). Install 16 AWG wire from each transistor to a common point.
d. Install the largest stud-mount SCR you can put in. I was aiming at a 135-ampere device. Bond it to the output terminals, and reference it back to the PC board.
e. Install a real meter shunt (another wirewound resistor mounted to the bottom of the case, suitably sized to drive the ammeter with an adjustment pot).
f. Complete installation of heavy-gauge wire everywhere in the DC power circuits between rectifiers, capacitor, pass transistors, SCR, and output terminals. Consider putting larger output terminals on rear of case.
As you can see, it really IS possible to make this supply a silk purse instead of a sow's ear; however, it's not clear to me that it's worth doing. You are talking somewhere between $50-$75 worth of parts to do a creditable job, and somewhere around 6-8 hours of labor. If your time is valuable to you, you'd be better off buying a new supply (or a used one) from somewhere else.
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KB1KVL
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Rating: 5/5
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Mar 6, 2006 18:25
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Can't ask for any better
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Time owned: more than 12 months
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This isn't PS53KX butis a PS-52KS and have had it 5 years. Have used it 12-14 hours a day with no problems whatsoever.
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N8EKT
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Rating: 1/5
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Apr 4, 2005 06:28
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NOT MADE WELL
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Time owned: more than 12 months
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I bought one of these because it was a few dollars less than the Astron.
BIG MISTAKE!
It failed and caused damage to my repeater system that resulted in a costly repair.
I replaced it with a Astron and have had no problems since.
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KB0IXM
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Rating: 0/5
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Feb 28, 2005 09:58
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Junk
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Time owned: 6 to 12 months
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Bought one of these brand new (not refurbished), hardly used it and had no load on it to speak of (25 watts). Within 3 months of purchase its putting out almost 20 volts. Nice way to ruin equipment. If your thinking about buying one don't waste your time or money, go with either an Astron or some other supply. I wouldnt wish this on my worst enemy. There's a reason they sell so cheap, you get what you pay for. Actually in this case I didn't even get that!
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KG6POG
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Rating: 4/5
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Feb 19, 2005 00:22
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PS-52KX
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Time owned: 6 to 12 months
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I use this power supply to run my Kenwood TS 480HX, and it does a fine job. No RF and powers the 200-watt radio without skipping a beat. I know I would probably be better off with a larger power supply, but this has done the trick without any problems for several months now and the only complaint is once in awhile the fan is a little noisy on start up.
The power supply is actually rated at 40 amp's continuous and 50 amps surge, so I'm not sure where they came up with the PS 52KX title for it. But the TS 480HX draws 41 amps on high power on FM CW and FSK, and so far it has done a fine job, never showing any signs of stress at all.
The reason I gave it 4 instead of 5 is because they give you the impression you’re buying a more powerful power supply.
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